Field
The present technology relates generally to enclosures for medical devices, and in particular, processes and components for sealing the enclosures.
Background
An enclosure for implantable medical devices may be configured from a pair of deep drawn titanium can halves that are laser welded together at a seam. An objective of the laser welded seam is to achieve a hermetic seal relative to the environment external to the device. Implantable medical devices are hermetically sealed to prevent the internal components from being damaged by moisture and to prevent injury to the patient that might be caused by the internal components.
Loss of hermeticity in an implanted medical device may result in a rapid increase of moisture within the device, resulting in an electrical short of internal components. An electrical short of internal components can result in one or more failure modes such as impaired device function, electrical shock of the implanted patient, or excessive heating of tissues in the implant area. Loss of hermeticity may also result in a material used inside the enclosure coming into unintended contact with patient tissue.
The laser welding process requires high density laser energy, sufficient to melt and fuse the titanium material of the top and bottom can halves. During the seam weld process, laser energy may pass through the seam between the abutting edges of each can half thereby presenting some risk to the internal components. For example, laser energy passing through the abutted edges of the top and bottom cans may vaporize internal components, e.g., plastic frames, which in turn, may result in a conductive residue further resulting in an electrical short of components. Laser energy passing through the abutted edges may also cause direct damage to temperature sensitive components such as the battery or soldered components on a printed circuit assembly. Damage to any of these components can result in a variety of failures ranging from impaired device function to serious injury or death to the patient.
Accordingly, to protect the internal components from being damaged during laser welding, a component is typically provided so that during laser welding, the component will obstruct the path of the laser beyond the desired location for the seam so that laser energy will not reach the internal components. The component also serves to capture molten metal, mitigating contact with internal components or a loose particulate within the device. The component used to provide the obstruction is sometimes referred to as a “backup band.” Other terms such as “weld ring,” or “weld band” are used to describe this type of component.